Urea-based carbon quantum dots for recognition of Fe3+ by fluorescence quenching and Pb2+ by fluorescence enhancement.

Abstract

The present study focuses on synthesis of Urea-based carbon quantum dots (UCQDs) using a non-toxic, low-cost hydrothermal method without consumption of any harmful chemical. The synthesized UCQDs were characterized via UV-Vis absorbance, Photoluminescence (PL), and FTIR spectroscopy. Distinct UV-Vis absorption peaks due to π-π* and n-π* transitions and existence of excitation-independent PL emission peaks at ~450 nm and ~525 nm, validated the presence of carbogenic core and nitrogen-enriched surface states. For water dissolved iron (Fe3+) ions UCQD proves its sensitivity by "Turn Off" fluorescence response, while it shows a "Turn On" sensing for Pb2+ ions. Bensei Hildebrand analysis, Stern-Volmer plots, Job plot and FTIR analysis established the sensing capability of UCQDs by the formation of UCQD: Metal ion complexation. The high quantum yield (~38%), high sensitivity and the low detection limit highlight UCQD's real life applicability for environmental pollution monitoring. The successful detection and quantification of metal ions in real samples validates UCQD  as potential future metal ion sensor.